Analysis of the mitochondrial proteome in multiple sclerosis cortex

Abstract

Mitochondrial dysfunction has been proposed to play a role in the neuropathology of multiple sclerosis (MS). Previously, we reported significant alterations in the transcription of nuclear-encoded electron transport chain genes in MS and confirmed translational alterations for components of Complexes I and III that resulted in reductions in their activity. To more thoroughly and efficiently elucidate potential alterations in the expression of mitochondrial and related proteins, we have characterized the mitochondrial proteome in postmortem MS and control cortex using Surface-Enhanced Laser Desorption Ionization Time of Flight Mass Spectrometry (SELDI-TOF-MS). Using principal component analysis (PCA) and hierarchical clustering techniques we were able to analyze the differential patterns of SELDI-TOF spectra to reveal clusters of peaks which distinguished MS from control samples. Four proteins in particular were responsible for distinguishing disease from control. Peptide fingerprint mapping unambiguously identified these differentially expressed proteins. Three proteins identified are involved in respiration including cytochrome c oxidase subunit 5b (COX5b), the brain specific isozyme of creatine kinase, and hemoglobin β-chain. The fourth protein identified was myelin basic protein (MBP). We then investigated whether these alterations were consistent in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. We found that MBP was similarly altered in EAE but the respiratory proteins were not. These data indicate that while the EAE mouse model may mimic aspects of MS neuropathology which result from inflammatory demyelinating events, there is another distinct mechanism involved in mitochondrial dysfunction in gray matter in MS which is not modeled in EAE.

Upregulation and Mitochondrial Sequestration of Hemoglobin Occur in Circulating Leukocytes during Critical Illness, Conferring a Cytoprotective Phenotype

“…Intracellular hemoglobin shows remarkable compartmentalization; it concentrates to the mitochondria, where it shows a particularly close association with mitochondrial complex I. It is interesting to note that a recent proteomic analysis of control brains and brains from multiple sclerosis patients has identified the mitochondrial localization of the hemoglobin β chain (30). The functional consequence of mitochondrial hemoglobin remains to be further elucidated; based on the current results, we speculate that it may either contribute to a specific mitochondrial protection (for example, against mitochondrial oxidative stress), or it may play a more specific role in the regulation of mitochondrial electron transport; the latter hypothesis is supported by our extracellular flux analysis findings indicating an increased basal and FCCP-uncoupled maximal rate of mitochondrial respiration in cells with increased mitochondrial hemoglobin content.…”

Role of autophagy in the pathogenesis of multiple sclerosis

“…Autophagy maintains the architecture of mitochondria, restores their function, and prevents their dysfunction, which are critical for cell survival and the pathogenesis of MS [21][22][23] . In MS, the decreased expression of cytochrome c oxidase subunit 5b may impair the function of mitochondria [24] . Dysfunction of mitochondria produces reactive oxygen species (ROS), which contribute to demyelination and axonal loss [25] .…”

Proteomic approaches to the study of renal mitochondria

“…The potential for utilization of protein microarrays in analysis of renal mitochondria could be in high throughput monitoring of selected pathways by analysis of multiple, predefined set of proteins. Arrays based on mass spectrometric detection of proteins bound to affinity surfaces (surface-enhanced laser desorption and ionization, SELDI) have been used for analysis of brain mitochondria 66,67 . Chips with wide range of surfaces are available for SELDI.…”